牙鲆幽门盲囊组织结构及黏液细胞的免疫应答特性

To understand the function of fish pyloric caeca and the response characteristics of mucous cells, in this study, the histological structure of the pyloric caeca, and types of mucous cells and their immune responses after vaccination were studied in flounder(Paralichthys olivaceus) by using histology, histochemistry, indirect immunofluorescence, qRT-PCR and ELISA techniques. The research showed that there were four blind tubes in the pyloric caeca, which consisted of mucosal, submucosal, muscular and serous layers from inside to outside, respectively. The mucosal epithelium contained four types of mucous cells, of which, the number of type Ⅱ mucous cells was the largest, type Ⅰ mucous cells took the second place, while the amount of type Ⅲ and Ⅳ mucous cells was very small. After injection of inactivated Edwardsiella tarda, the types and numbers of mucous cells changed significantly. The number of type Ⅰ mucous cells was reduced while type Ⅱ, Ⅲ and Ⅳ mucous cells were increased. Also, the total number of mucous cells was increased, peaked on the 3rd day after immunization, and the proliferation of mucous cells could be observed on the 2nd to 3rd day. The mucous cells of the pyloric caeca of flounder could express mucin Muc2 gene, but not Muc5ac gene. Post immunization, mucin Muc2 and its gene transcript in the pyloric caeca first increased and then decreased, and the muc2 transcripts peaked at 48 h while the Muc2 protein peaked at 24 h. These results revealed that vaccine immunization induced changes in the types of the mucous cells in the pyloric caeca of flounder, and increases of the number of mucous cells and the expression of mucin Muc2 gene, indicating that the mucus barrier was strengthened. These findings provided a theoretical reference for further understanding the immune defense function of fish pyloric caeca and the crucial role of mucous cells in fish mucosal immunity.